DOCSLIB.ORG

Star Formation History and Environment of the Dwarf Galaxy

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Star Formation History and Environment of the Dwarf Galaxy Mon. Not. R. Astron. Soc. 000, 1–11 (XXX) Printed 12 November 2018 (MN LATEX style file v2.2) Star formation history and environment of the dwarf galaxy UGCA92⋆ Lidia Makarova1,2†, Dmitry Makarov1,2,3, Sergey Savchenko4 1Special Astrophysical Observatory, Nizhniy Arkhyz, Karachai-Cherkessia 369167, Russia 2Isaac Newton Institute of Chile, SAO Branch, Russia 3Universit´eLyon 1, Villeurbanne, F-69622, France; CRAL, Observatoire de Lyon, St. Genis Laval, F-69561, France 4Astronomical Institute, Saint-Petersburg State University, Saint-Petersburg, Russia Accepted XXX. Received XXX; in original form XXX ABSTRACT We present a quantitative star formation history of the nearby dwarf galaxy UGCA 92. This irregular dwarf is situated in the vicinity of the Local Group of galaxies in a zone of strong Galactic extinction (IC 342 group of galaxies). The galaxy was resolved into stars with HST/ACS including old red giant branch. We have constructed a model of the resolved stellar populations and measured the star formation rate and metallicity as function of time. The main star formation activity period occurredabout 8 – 14 Gyr ago. These stars are mostly metal-poor, with a mean metallicity [Fe/H] ∼−1.5– −2.0 dex. About 84 percent of the total stellar mass was formed during this event. There are also indications of recent star formation starting about 1.5 Gyr ago and continuing to the present. The star formation in this event shows moderate enhancement from ∼ 200 Myr to 300 Myr ago. It is very likely that the ongoing star formation period has higher metallicity of about −0.6 – −0.3 dex. UGCA92 is often considered to be the companion to the starburst galaxy NGC1569. Comparing our star formation history of UGCA92 with that of NGC1569 reveals no causal or temporal connection between recent star formation events in these two galaxies. We suggest that the starburst phenomenon in NGC 1569 is not related to the galaxy’s closest dwarf neighbours and does not affect their star formation history. Key words: galaxies: dwarf – galaxies: formation – galaxies: evolution – galaxies: stellar content – galaxies: individual: UGCA 92 arXiv:1203.1397v1 [astro-ph.CO] 7 Mar 2012 1 INTRODUCTION into account loose associations of dwarf galaxies (Tully et al. 2006), most of the galaxies within 3 Mpc are not isolated ob- Dwarf galaxies are most numerous objects in the Universe. jects. The nearby group around IC 342 is obscured by strong The question of star formation in dwarf galaxies is extremely Galactic extinction (see Fig. 1). The IC 342-Maffei complex important for understanding of their origin and evolution. should have significant impact on dynamic and evolution The local Universe (610 Mpc) is particularly important and of the nearby Universe. Unfortunately, the ‘Zone of Avoid- convenient for studying dwarf galaxies. Nearby galaxies are ance’ hides this region from us and a determination of main resolved into individual stars, which allow us to study stel- properties of galaxies behind it is a challenge. lar population of these galaxies directly. In the last decades, significant progress has been achieved in the study of re- In the framework of the study of the structure of the solved stellar populations due to the Hubble Space Telescope nearby Universe (HST project 9771) we have obtained the (HST ) and new large ground-based telescopes. images of dwarf galaxies within IC 342/Maffei complex. In About 50 per cent of nearby galaxies are situated in the present work we have considered the star formation his- groups and clouds (Makarov & Karachentsev 2011). Taking tory of the dwarf irregular galaxy UGCA 92, which has for a long time been considered to be the closest neighbour of the nearest starburst galaxy NGC 1569 (Karachentsev et al. ⋆ Based on observations made with the NASA/ESA Hubble 1994b; Makarova & Karachentsev 2003). Space Telescope, obtained from the data archive at the Space Telescope Science Institute. STScI is operated by the Associa- The small irregular galaxy UGCA 92 was discovered by tion of Universities for Research in Astronomy, Inc. under NASA Nilson (1974) and independently catalogued as a possible contract NAS 5-26555. planetary nebula by Ellis et al. (1984). CCD observations † E-mail: [email protected] of Hoessel et al. (1988) partially resolving it into individ- c XXX RAS 2 Makarova et al. Figure 1. Location of the IC 342/Maffei complex of galaxies in Galactic coordinates. Colours denote galaxy type. The IRAS extinction map is shown in grey scale. ual stars in the g and r passband images first showed that Table 1. General parameters of UGCA 92. UGCA 92 (EGB 0427+63) is a dwarf irregular galaxy. Hodge h m s & Miller (1995) detected 25 H ii regions within UGCA 92, R.A.(J2000) 04 32 03.5 [2] Dec (J2000) +63◦36′58′′ [2] concentrated in two well-separated regions of the galaxy. The reddening, measured from the emission-line spectra for size, arcmin 2.0 × 1.0 [3] bright H ii regions is E(B − V ) = 0.90 ± 0.08 and the mean Linear diameter, kpc 3.1 [1] oxygen abundance is about 13 per cent solar, with an uncer- (m − M)0, mag 27.41 ± 0.25 [1] tainty of 50 per cent. Karachentsev & Kaisin (2010) carried Distance, Mpc 3.03 ± 0.35 [1] out Hα flux measurement for UGCA 92 and derived a cur- BT , mag 15.22 [4] rent star formation rate of log(SFR) = −1.51 M⊙/yr. (B − V )T , mag 1.34 [4] The general parameters of UGCA 92 are presented in V3′ , mag 14.55 [5] Table 1. The total magnitudes, colours and central surface I3′ , mag 12.87 [5] JT , mag 12.38 [6] brightnesses, µ(0), are not corrected for Galactic extinction. KsT , mag 11.12 [6] −2 µ(0)B , mag arcsec 25.1 [4] −2 µ(0)V , mag arcsec 24.18 ± 0.01 [5] −2 2 THE DATASET µ(0)I , mag arcsec 22.61 ± 0.01 [5] E(B − V ), mag 0.79 ± 0.13 [7] The dwarf irregular galaxy UGCA 92 was observed aboard AI , mag 1.54 ± 0.25 [7] HST using Advanced Camera for Surveys (ACS) at March −1 28, 2004 (SNAP 9771, PI I. Karachentsev). Two exposures VLG, kms 93 [8] MB, mag −15.61 [1] were made with the filters F606W (1200 s) and F814W (900 8 MHI , M⊙ 1.56 × 10 [8] s). An ACS image of the dwarf galaxy is shown in Fig. 2. MHI /LB 0.55 [8] The photometry of resolved stars in the galaxy was per- 1 Fraction of old stars (12–14 Gyr), % 84 ± 7 [1] formed with the ACS module of the dolphot package for Metallicity of old stars, [Fe/H], dex −2.0 – −1.5 [1] crowded field photometry (Dolphin 2002) using the recom- Fraction of young stars (500 Myr), % 7.6 ± 0.7 [1] −1 −1 mended recipe and parameters. Only stars with photometry hSFRi, 12 – 14 Gyr ago, M⊙ yr 1.2 ± 0.1 × 10 [1] −1 −2 of good quality were included in the final list, following rec- hSFRi, last 500 Myr, M⊙ yr 4.3 ± 0.6 × 10 [1] ommendations given in the dolphot User’s Guide. We have selected stars with signal-to-noise (S/N) > 5 in both filters, [1] this work; [2] LEDA; [3] Karachentsev et al. (2004); 2 [4] Karachentseva et al. (1996); [5] Sharina et al. (2008); χ 6 2.5 and |sharp| 6 0.3. The resulting colour-magnitude [6] Vaduvescu et al. (2005); [7] Schlegel et al. (1998); [8] Be- diagram contains 32699 stars (Fig. 3). gum et al. (2008) Artificial star tests were performed using the same re- duction procedures to estimate photometric errors, crowd- edness and blending effects in the most accurate way. A large library of artificial stars was generated spanning the necessary range of stellar magnitudes and colours so that the distribution of the recovered photometry is adequately 1 http://purcell.as.arizona.edu/dolphot/ sampled. The photometric errors and completeness are pre- c XXX RAS, MNRAS 000, 1–11 Star formation history of UGCA92 3 Figure 2. HST /ACS image of UGCA 92 in F606W filter. The image size is 3.4 × 3.4 arcmin. 19 20 21 22 23 24 25 26 27 28 29 16 18 20 22 24 26 28 1 1 0.8 0.8 0.6 0.6 0.4 0.4 completeness 0.2 completeness 0.2 0 0 −1 −0.5 −0.5 , mag , mag ∆ ∆ 0 0 0.5 0.5 19 20 21 22 23 24 25 26 27 28 29 16 18 20 22 24 26 28 F606W, mag F814W, mag Figure 4. Photometric errors and completeness for UGCA 92. The top panels show the completeness, i.e. the fraction of artificial stars recovered within the photometric reduction procedure, as a function of the F606W and F814W magnitudes. The bottom panels give the difference between the measured and the true input magnitude (∆mag = measure − input). The error bars are 1 σ residuals. sented in Fig. 4. The 1 σ photometric precision is 0.07 at 3 COLOUR-MAGNITUDE DIAGRAM F814W = 25 and 0.19 at F814W = 27 mag. Malmquist bias becomes notable for stars with F814W > 26.8 mag. In All resolved stars are significantly shifted to redder colours F606W the 1 σ photometric precision is 0.06 at 26 and 0.18 due to high extinction in the Zone of Avoidance of the at 28 mag. Milky Way. The diagram is typical for dwarf irregular galax- ies. A pronounced upper main sequence (MS) and proba- ble helium-burning blue loop stars are found at F606W − c XXX RAS, MNRAS 000, 1–11 4 Makarova et al.
Load more

Recommended publications
  • Dwarf Galaxies: Probes for Galaxy Formation and Evolution
    JD2 Dwarf Galaxies: Probes for Galaxy Formation and Evolution Chairpersons and Editors: E. Brinks &; T. X. Thuan Downloaded from https://www.cambridge.org/core. IP address: 170.106.40.139, on 30 Sep 2021 at 22:48:50, subject to the Cambridge Core terms of use, available at https://www.cambridge.org/core/terms. https://doi.org/10.1017/S1539299600020074 MULTI-SPECTRAL STUDIES OF THE NEARBY DWARF GALAXIES UGCA86 AND LMC/SMC G. M. RICHTER Astrophysikalisches Institut Potsdam An der Sternwarte 16, D-14482 Potsdam, Germany gmrichter@aip. de M. BRAUN ESA-VILSPA ISOPHOT IDT Villafranca del Castillo, Satellite Tracking Station Apartado 50727, E-28080 Madrid, Spain [email protected] AND R. ASSENDORP Astrophysikalisches Institut Potsdam An der Sternwarte 16, D-14482 Potsdam, Germany rassendorp @aip. de 1. Background UGCA 86 is an irregular dwarf galaxy in the IC 342 / Maffei I group, just next to the Local Group. It was first mentioned by Zwicky (1968) as VII Zw 009, but not contained in his "Catalogue of Selected Compact Galaxies and of Post-eruptive Galaxies" (1971). It was independently rediscovered by Nilson (1974) and Rots (1979) as UGCA 86 and A 0355 resp. Rots found it by HI observations, and from peculiarities in the HI morphology and kinematics he suspected that it was interacting with IC 342. Thus, the tentatively interesting items: a starforming, low surface brightness dwarf galaxy in an interacting system (one of the nearest), triggered us to engage in more detailed studies. In a first step, we made detailed surface photometry in U, B and V (Richter et al.
    [Show full text]
  • CO Multi-Line Imaging of Nearby Galaxies (COMING) IV. Overview Of
    Publ. Astron. Soc. Japan (2018) 00(0), 1–33 1 doi: 10.1093/pasj/xxx000 CO Multi-line Imaging of Nearby Galaxies (COMING) IV. Overview of the Project Kazuo SORAI1, 2, 3, 4, 5, Nario KUNO4, 5, Kazuyuki MURAOKA6, Yusuke MIYAMOTO7, 8, Hiroyuki KANEKO7, Hiroyuki NAKANISHI9 , Naomasa NAKAI4, 5, 10, Kazuki YANAGITANI6 , Takahiro TANAKA4, Yuya SATO4, Dragan SALAK10, Michiko UMEI2 , Kana MOROKUMA-MATSUI7, 8, 11, 12, Naoko MATSUMOTO13, 14, Saeko UENO9, Hsi-An PAN15, Yuto NOMA10, Tsutomu, T. TAKEUCHI16 , Moe YODA16, Mayu KURODA6, Atsushi YASUDA4 , Yoshiyuki YAJIMA2 , Nagisa OI17, Shugo SHIBATA2, Masumichi SETA10, Yoshimasa WATANABE4, 5, 18, Shoichiro KITA4, Ryusei KOMATSUZAKI4 , Ayumi KAJIKAWA2, 3, Yu YASHIMA2, 3, Suchetha COORAY16 , Hiroyuki BAJI6 , Yoko SEGAWA2 , Takami TASHIRO2 , Miho TAKEDA6, Nozomi KISHIDA2 , Takuya HATAKEYAMA4 , Yuto TOMIYASU4 and Chey SAITA9 1Department of Physics, Faculty of Science, Hokkaido University, Kita 10 Nishi 8, Kita-ku, Sapporo 060-0810, Japan 2Department of Cosmosciences, Graduate School of Science, Hokkaido University, Kita 10 Nishi 8, Kita-ku, Sapporo 060-0810, Japan 3Department of Physics, School of Science, Hokkaido University, Kita 10 Nishi 8, Kita-ku, Sapporo 060-0810, Japan 4Division of Physics, Faculty of Pure and Applied Sciences, University of Tsukuba, 1-1-1 Tennodai, Tsukuba, Ibaraki 305-8571, Japan 5Tomonaga Center for the History of the Universe (TCHoU), University of Tsukuba, 1-1-1 Tennodai, Tsukuba, Ibaraki 305-8571, Japan 6Department of Physical Science, Osaka Prefecture University, Gakuen 1-1,
    [Show full text]
  • Science in the Urantia Papers
    Science ¾ Scientific Validation of the UB z By Denver Pearson z By Phil Calabrese ¾ Seraphic Velocities ¾ Astronomy The Scientific Integrity of the Urantia Book by Denver Pearson As scientifically minded readers first peruse the Urantia Book, it soon occurs to them that many of its statements on the natural sciences conflict with currently held data and theories. In the minds of many this gives rise to doubts about the truthfulness of those statements. Wisdom would lead us to realize that nothing short of perfection is perfect, and anything touched by human hands has fingerprints. This should be our guiding thoughts as we contemplate the accuracy of the scientific content of the Urantia Papers. Several years ago, at the first scientific symposium, it was implied by one of the speakers that the revelation contains errors. This implication is alarming. More recently, at the second symposium held in Oklahoma, an interesting publication named "The Science Content of The Urantia Book" was made available (this document is obtainable from the Brotherhood of Man Library). In this publication is an article entitled "Time Bombs" in which the author suggests that the revelators planted certain inaccurate scientific statements in the book in order to prevent it from becoming a fetish. He states "...the revelators incorporated safeguards in the papers that would form The Urantia Book to diminish the tendency to regard it as an object of worship. What safeguards did they use? Suppose they decided to make sure that mortals reading it understood that some cosmological statements in the book would be found to be inaccurate".
    [Show full text]
  • ASTRONOMY and ASTROPHYSICS the Elliptical Galaxy Formerly Known As the Local Group: Merging the Globular Cluster Systems
    Astron. Astrophys. 358, 471–480 (2000) ASTRONOMY AND ASTROPHYSICS The elliptical galaxy formerly known as the Local Group: merging the globular cluster systems Duncan A. Forbes1,2, Karen L. Masters1, Dante Minniti3, and Pauline Barmby4 1 University of Birmingham, School of Physics and Astronomy, Edgbaston, Birmingham B15 2TT, UK 2 Swinburne University of Technology, Astrophysics and Supercomputing, Hawthorn, Victoria 3122, Australia 3 P. Universidad Catolica,´ Departamento de Astronom´ıa y Astrof´ısica, Casilla 104, Santiago 22, Chile 4 Harvard–Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138, USA Received 5 November 1999 / Accepted 27 January 2000 Abstract. Prompted by a new catalogue of M31 globular clus- al. 1995; Minniti et al. 1996). Furthermore Hubble Space Tele- ters, we have collected together individual metallicity values for scope studies of merging disk galaxies reveal evidence for the globular clusters in the Local Group. Although we briefly de- GC systems of the progenitor galaxies (e.g. Forbes & Hau 1999; scribe the globular cluster systems of the individual Local Group Whitmore et al. 1999). Thus GCs should survive the merger of galaxies, the main thrust of our paper is to examine the collec- their parent galaxies, and will form a new GC system around tive properties. In this way we are simulating the dissipationless the newly formed elliptical galaxy. merger of the Local Group, into presumably an elliptical galaxy. The globular clusters of the Local Group are the best studied Such a merger is dominated by the Milky Way and M31, which and offer a unique opportunity to examine their collective prop- appear to be fairly typical examples of globular cluster systems erties (reviews of LG star clusters can be found in Brodie 1993 of spiral galaxies.
    [Show full text]
  • The Triggering of Starbursts in Low-Mass Galaxies
    Mon. Not. R. Astron. Soc. 000, 000{000 (0000) Printed 28 September 2018 (MN LATEX style file v2.2) The triggering of starbursts in low-mass galaxies Federico Lelli1;2 ?, Marc Verheijen2, Filippo Fraternali3;1 1Department of Astronomy, Case Western Reserve University, 10900 Euclid Ave, Cleveland, OH 44106, USA 2Kapteyn Astronomical Institute, University of Groningen, Postbus 800, 9700 AV, Groningen, The Netherlands 3Department of Physics and Astronomy, University of Bologna, via Berti Pichat 6/2, 40127, Bologna, Italy ABSTRACT Strong bursts of star formation in galaxies may be triggered either by internal or ex- ternal mechanisms. We study the distribution and kinematics of the H I gas in the outer regions of 18 nearby starburst dwarf galaxies, that have accurate star-formation histories from HST observations of resolved stellar populations. We find that star- burst dwarfs show a variety of H I morphologies, ranging from heavily disturbed H I distributions with major asymmetries, long filaments, and/or H I-stellar offsets, to lop- sided H I distributions with minor asymmetries. We quantify the outer H I asymmetry for both our sample and a control sample of typical dwarf irregulars. Starburst dwarfs have more asymmetric outer H I morphologies than typical irregulars, suggesting that some external mechanism triggered the starburst. Moreover, galaxies hosting an old burst (&100 Myr) have more symmetric H I morphologies than galaxies hosting a young one (.100 Myr), indicating that the former ones probably had enough time to regularize their outer H I distribution since the onset of the burst. We also investigate the nearby environment of these starburst dwarfs and find that most of them (∼80%) have at least one potential perturber at a projected distance .200 kpc.
    [Show full text]
  • An Observational Limit on the Dwarf Galaxy Population of the Local Group
    An Observational Limit on the Dwarf Galaxy Population of the Local Group Alan B. Whiting1 Cerro Tololo Inter-American Observatory Casilla 603, La Serena, Chile [email protected] George K. T. Hau University of Durham Mike Irwin University of Cambridge Miguel Verdugo Institut f¨ur Astrophysik G¨ottingen, Germany ABSTRACT We present the results of an all-sky, deep optical survey for faint Local Group dwarf galaxies. Candidate objects were selected from the second Palomar survey (POSS-II) and ESO/SRC survey plates and follow-up observations performed to determine whether they were indeed overlooked members of the Local Group. arXiv:astro-ph/0610551v1 18 Oct 2006 Only two galaxies (Antlia and Cetus) were discovered this way out of 206 candi- dates. Based on internal and external comparisons, we estimate that our visual survey is more than 77% complete for objects larger than one arc minute in size and with a surface brightness greater than an extremely faint limit over the 72% of the sky not obstructed by the Milky Way. Our limit of sensitivity cannot be calculated exactly, but is certainly fainter than 25 magnitudes per square arc second in R, probably 25.5 and possibly approaching 26. We conclude that there are at most one or two Local Group dwarf galaxies fitting our observational cri- teria still undiscovered in the clear part of the sky, and roughly a dozen hidden behind the Milky Way. Our work places the “missing satellite problem” on a firm quantitative observational basis. We present detailed data on all our candidates, including surface brightness measurements.
    [Show full text]
  • Dwarf Galaxies of the Local Group Offer the Best Opportunity to Study a Representative Sample of These Important, but by Nature, Inconspicuous Galaxies in Detail
    DWARF GALAXIES OF THE LOCAL GROUP Mario Mateo KEY WORDS: Stellar Populations, Local Group Galaxies, Photometry, Galaxy Formation, Spectroscopy, Dark Matter, Interstellar Medium Shortened Title: LOCAL GROUP DWARFS Send Proofs To: Mario Mateo Department of Astronomy; University of Michigan Ann Arbor, MI 48109-1090 Phone: 313 936-1742; Fax: 313 763-6317 Email: [email protected] ABSTRACT The Local Group (LG) dwarf galaxies offer a unique window to the detailed properties of the most common type of galaxy in the Universe. In this review, I update the census of LG dwarfs based on the most recent distance and radial velocity determinations. I then discuss the detailed properties of this sample, including (a) the integrated photometric parameters and optical structures of these galaxies, (b) the content, nature and distribution of their ISM, (c) their heavy-element abundances derived from both stars and nebulae, (d) the arXiv:astro-ph/9810070v1 5 Oct 1998 complex and varied star-formation histories of these dwarfs, (e) their internal kinematics, stressing the relevance of these galaxies to the dark-matter problem and to alternative interpretations, and (f) evidence for past, ongoing and future interactions of these dwarfs with other galaxies in the Local Group and beyond. To complement the discussion and to serve as a foundation for future work, I present an extensive set of basic observational data in tables that summarize much of what we know, and what we still do not know, about these nearby dwarfs. Our understanding of these galaxies has grown impressively in the past decade, but fundamental puzzles remain that will keep the Local Group at the forefront of galaxy evolution studies for some time.
    [Show full text]
  • Making a Sky Atlas
    Appendix A Making a Sky Atlas Although a number of very advanced sky atlases are now available in print, none is likely to be ideal for any given task. Published atlases will probably have too few or too many guide stars, too few or too many deep-sky objects plotted in them, wrong- size charts, etc. I found that with MegaStar I could design and make, specifically for my survey, a “just right” personalized atlas. My atlas consists of 108 charts, each about twenty square degrees in size, with guide stars down to magnitude 8.9. I used only the northernmost 78 charts, since I observed the sky only down to –35°. On the charts I plotted only the objects I wanted to observe. In addition I made enlargements of small, overcrowded areas (“quad charts”) as well as separate large-scale charts for the Virgo Galaxy Cluster, the latter with guide stars down to magnitude 11.4. I put the charts in plastic sheet protectors in a three-ring binder, taking them out and plac- ing them on my telescope mount’s clipboard as needed. To find an object I would use the 35 mm finder (except in the Virgo Cluster, where I used the 60 mm as the finder) to point the ensemble of telescopes at the indicated spot among the guide stars. If the object was not seen in the 35 mm, as it usually was not, I would then look in the larger telescopes. If the object was not immediately visible even in the primary telescope – a not uncommon occur- rence due to inexact initial pointing – I would then scan around for it.
    [Show full text]
  • Popular Names of Deep Sky (Galaxies,Nebulae and Clusters) Viciana’S List
    POPULAR NAMES OF DEEP SKY (GALAXIES,NEBULAE AND CLUSTERS) VICIANA’S LIST 2ª version August 2014 There isn’t any astronomical guide or star chart without a list of popular names of deep sky objects. Given the huge amount of celestial bodies labeled only with a number, the popular names given to them serve as a friendly anchor in a broad and complicated science such as Astronomy The origin of these names is varied. Some of them come from mythology (Pleiades); others from their discoverer; some describe their shape or singularities; (for instance, a rotten egg, because of its odor); and others belong to a constellation (Great Orion Nebula); etc. The real popular names of celestial bodies are those that for some special characteristic, have been inspired by the imagination of astronomers and amateurs. The most complete list is proposed by SEDS (Students for the Exploration and Development of Space). Other sources that have been used to produce this illustrated dictionary are AstroSurf, Wikipedia, Astronomy Picture of the Day, Skymap computer program, Cartes du ciel and a large bibliography of THE NAMES OF THE UNIVERSE. If you know other name of popular deep sky objects and you think it is important to include them in the popular names’ list, please send it to [email protected] with at least three references from different websites. If you have a good photo of some of the deep sky objects, please send it with standard technical specifications and an optional comment. It will be published in the names of the Universe blog. It could also be included in the ILLUSTRATED DICTIONARY OF POPULAR NAMES OF DEEP SKY.
    [Show full text]
  • A Unified Formation Scenario for the Zoo of Extended Star Clustersand Ultra-Compact Dwarf Galaxies
    A UNIFIED FORMATION SCENARIO FOR THE ZOO OF EXTENDED STAR CLUSTERS AND ULTRA-COMPACT DWARF GALAXIES DISSERTATION zur Erlangung des Doktorgrades (Dr. rer. nat.) der Mathematisch-Naturwissenschaftlichen Fakultät der Rheinischen Friedrich-Wilhelms-Universität Bonn vorgelegt von RENATE CLAUDIA BRÜNS aus Bonn Bonn, 2013 Angefertigt mit Genehmigung der Mathematisch-Naturwissenschaftlichen Fakultät der Rheinischen Friedrich-Wilhelms-Universität Bonn 1. Gutachter: Prof. Dr. P. Kroupa 2. Gutachter: Prof. Dr. U. Klein Tag der Promotion: 16. Juni 2014 Erscheinungsjahr: 2014 Contents Abstract 1 1 Introduction 3 1.1 Old Star Clusters in the Local Group ......................... 3 1.2 Old Star Clusters beyond the Local Group ..................... 7 1.3 Ultra-Compact Dwarf Galaxies ............................ 8 1.4 Young Massive Star Clusters and Star Cluster Complexes ............. 9 1.5 Outline of Thesis .................................... 14 2 NumericalMethod 17 2.1 N-BodyCodes ..................................... 17 2.1.1 Set-Up of the Initial Conditions ....................... 18 2.1.2 The Integrator ................................. 22 2.1.3 Determination of Accelerations from the N Particles ............ 23 2.1.4 The Analytical External Tidal Field ..................... 26 2.1.5 Determination of the Enclosed Mass and the Effective Radius ...... 29 2.2 The Particle-Mesh Code SUPERBOX ......................... 29 2.2.1 Definition of the Grids and the Determination of Accelerations ...... 30 2.2.2 Illustration of the Combination of the Grid Potentials ........... 32 2.2.3 General Framework for the Choice of Parameters for the Simulations . 34 2.2.4 SUPERBOX++ versus Fortran SUPERBOX ................... 40 3 ACatalogofECsandUCDsinVariousEnvironments 43 3.1 Introduction ...................................... 43 3.2 The Observational Basis of the EO Catalog ..................... 44 3.2.1 EOs in Late-Type Galaxies .........................
    [Show full text]
  • ”Scraggy” Dark Halos Around Bulge-Less Spiral Galaxies 3
    MNRAS 000, 1–?? (XXX) Preprint 1 May 2019 Compiled using MNRAS LATEX style file v3.0 ”Scraggy” dark halos around bulge-less spiral galaxies I. D. Karachentsev1⋆, V. E. Karachentseva2 1Special Astrophysical Observatory, Russian Academy of Sciences, N.Arkhyz, 369167 Russia 2Main Astronomical Observatory of National Academy of Sciences of Ukraine, Kiev, 03143 Ukraine Accepted XXX. Received XXX; in original form XXX ABSTRACT We use a sample of 220 face-on bulge-less galaxies situated in the low density environment to estimate their total mass via orbital motions of supposed rare satellites. Our inspection reveals 43 dwarf companions having the mean projected separation of 130 kpc and the mean-square velocity difference of 96 km/s. For them, we obtain the mean orbital-mass-to-K-band luminosity ratio of 20 ± 3. Seven bulge-less spirals in the Local Volume are also characterized by the low mean ratio, Morb/LK = 22 ± 5. We conclude that bulge-less Sc-Scd-Sd galaxies have poor dark halos, about two times lower than that of bulgy spiral galaxies of the same stellar mass. Key words: galaxies: bulges – galaxies: spiral – galaxies 1 INTRODUCTION. 10 Among the galaxies with stellar masses of more than, 10 M⊙ the flat disc-like objects without the evidence of the central bulge constitute about 10%. Almost all of them are classified as late-type spirals: Sc, Scd, and Sd according to de Vaucouleurs et al. (1976). Some of them demonstrate small pseudo-bulges formed during the process of the secular disc evolution. Unlike classical bulges, the pseudo-bulges show a nearly exponent stellar density profile and the evidences of current star formation (Kormendy & Kennicutt 2004).
    [Show full text]
  • ALABAMA University Libraries
    THE UNIVERSITY OF ALABAMA University Libraries The IC 342/Maffei Group Revealed Ronald J. Buta – University of Alabama Marshall L. McCall – York University, Canada Deposited 06/11/2019 Citation of published version: Buta, R., McCall, M. (1999): The IC 342/Maffei Group Revealed. The Astrophysical Journal Supplement Series, 124(1). DOI: 10.1086/313255 © 1999. The American Astronomical Society. All rights reserved. THE ASTROPHYSICAL JOURNAL SUPPLEMENT SERIES, 124:33È93, 1999 September ( 1999. The American Astronomical Society. All rights reserved. Printed in U.S.A. THE IC 342/MAFFEI GROUP REVEALED RONALD J. BUTA1 University of Alabama Department of Physics and Astronomy, Tuscaloosa, AL 35487-0324; buta=sarah.astr.ua.edu AND MARSHALL L. MCCALL1,2 York University Department of Physics and Astronomy, 4700 Keele Street, Toronto, Ontario, Canada, M3J 1P3; mccall=yorku.ca Received 1998 November 30; accepted 1999 April 27 ABSTRACT Deep wide-Ðeld CCD images in the optical and near-infrared have been acquired for 14 of the 16 known or suspected members of the IC 342/Ma†ei Group of galaxies, one of the closest groups to the Milky Way, and probably the closest group to M31. Because of their low Galactic latitude, all galaxies are heavily extinguished, and myriads of foreground stars are superimposed. A sophisticated algorithm built around DAOPHOT has been developed which successfully removes the foreground stars, making possible comprehensive morphological and photometric studies. The cleaned near-infrared images reveal the true morphology and extent of many of the galaxies for the Ðrst time, three of which are among the largest in the northern sky.
    [Show full text]